A sheet punching apparatus should be operated in such a manner that sheets are punched at the same position for exact alignment.
However, the punching position per sheet may be varied due to deviation or distortion in the position of feeding sheets. Ends of punched sheets may not be aligned exactly.
To solve such problems, a related art sheet punching apparatus is disclosed in Japanese Patent Publication No. 2002-200593. In this related art, the end position of sheets is sensed by a sensor and a punch portion of a sheet punching apparatus is moved in a width direction of sheets in accordance with the sensed result to adjust the position of the punch portion, thereby enabling punching of the sheets at the center in the width direction of sheets.
The related art sheet punching apparatus will be described with reference to FIGS. 1 and 2.
The sheet punching apparatus 1 is arranged along a direction perpendicular to a feeding direction of a sheet S. The sheet punching apparatus 1 includes a male punch 2 and a female punch 3. The female punch 3 is arranged below the male punch 2 to oppose the male punch 2 around a feeding path D of the sheet S. In the male punch 2, a rotary shaft 4 is fixed to a support 5 in a direction perpendicular to the feeding direction of the sheet S. The rotary shaft 4 is provided with a cam 6 that adjoins the top of the male punch 2. The top of the male punch 2 adjoins the cam 6 by means of an elastic support (not shown).
In the aforementioned related sheet punching apparatus, the face of the cam 6 pushes the top of the male punch 2 as the rotary shaft 4 rotates. As a result, the male punch 2 is moved to the female punch 3 so that a predetermined position of the sheet S is punched.
An upper guide 7a constituting a sheet guide portion along the upper side of the feeding path P of the sheet S is disposed below the male punch 2. A lower guide 7b is disposed above the female punch 3 to facilitate guide of the sheet.
In the aforementioned related art punching apparatus, the male punch 2, the female punch 3, the rotary shaft 4, and the upper and lower guides 7a and 7b are fixed to the support 5 in a single body.
A rack gear 8 is provided at one end of the support 5. The rack gear 8 is engaged with a pinion gear 10 provided in a driving motor 9. Once the driving gear 9 rotates in a forward or reverse direction, the driving force is transmitted to the sheet punching apparatus 1 through the pinion gear 10 and the rack gear 8. Thus, the sheet punching apparatus 1 is moved to the direction perpendicular to the feeding direction of the sheet S.
In the aforementioned related art sheet punching apparatus, a sheet sensing means 11 is provided to sense the side and the end parallel to the feeding direction of the sheet S.
The sheet sensing means 11 includes reflecting photo sensors S1, S2, S3, S4, and S5 provided in the upper guide 7a along the direction perpendicular to the feeding direction of the sheet S to correspond to the width of various sized sheets to be punched.
The upper guide 7a is provided with a receiving hole 12 corresponding to the sensors S1˜S5. The respective sensors S1˜S5 transmit light to the lower guide 7b through the receiving hole 12 and sense the side end of the sheet S by means of the intensity of the reflecting light.
That is, once the sheet punching apparatus 1 moves to an arrow of FIG. 2, the sheet sensing means 11 provided in the upper guide 7a is moved from the inner side of the side end of the sheet S to its outer side. At this time, the side end of the sheet S is sensed by the intensity of the reflecting light and the punching apparatus is moved to the punching position in accordance with the sensed result.
As aforementioned, since the sheet sensing means 11 moving along with the sheet punching apparatus is provided in the sheet punching apparatus, the whole moving amount is small and punching efficiency can be improved. However, there are still problems. That is, a separate sensor that senses a hole position of the punching apparatus is required and the sensor provided in the punching apparatus cannot sense whether the punching apparatus is detached or not.